Automatic offsets - Paid supplier invoices

Issue: 

We are using automatic offsets in our system - there are a few expenditure items which have not been burdened, noticed that the supplier invoices in AP have been paid prior to the expenditure item date in projects and hence system is unable to calculate the burden cost and cost distribute the transactions.

Example :  AP invoice paid on Jan 22nd 2011

                   Expenditure item date in Projects  Mar 19 2011

In Mar PA period the item does not cost distribute as the supplier invoice related to the item has been paid off.

Solution: Please suggest a solution to burden these kind of transactions